Expandable resins

Abstract

Resin beads having an average particle size of from 0.001 mm to 10 mm and containing a continuous phase and a particulate dispersed phase are described. The continuous phase includes elastomeric polymers; the dispersed phase includes homopolymers and/or copolymers containing repeat units resulting from the polymerization of one or more aryl polymerizable monomers. The unexpanded polymer resin beads can be prepared by dispersing an organic phase containing elastomeric polymers and one or more monomers, into droplets and polymerizing the monomers in the organic droplets in a low shear flow pattern. The beads can be impregnated with blowing agents, expanded and can be used to make molded articles. Resin beads having a continuous phase comprising a nitrile rubber, and a dispersed phase comprising one or more homopolymers and/or copolymers containing repeat units resulting form the polymerization of one or more aryl polymerizable show prolonged retention of blowing agents in unexpanded form.

1. An unexpanded resin bead having an average particle size of from 0.001 mm to 10 mm and comprising a continuous phase and a particulate dispersed phase, wherein
 the continuous phase comprises one or more elastomeric polymers, and 
 the dispersed phase comprises one or more homopolymers and/or copolymers containing repeat units resulting from the polymerization of one or more aryl polymerizable monomers; and 
 wherein the resin bead comprises a skin covering an outer surface of the resin bead; and 
 wherein the skin comprises the homopolymers and/or copolymers of the dispersed phase. 
 
     
     
       2. The resin bead according to  claim 1 , wherein the particulate dispersed phase comprises particles having an aspect ratio of from 1 to 10. 
     
     
       3. The resin bead according to  claim 1 , wherein the particulate dispersed phase comprises particles having a circular, oval or elliptical cross-section shape. 
     
     
       4. The resin bead according to  claim 1 , wherein the continuous phase has a crosslinked web morphology. 
     
     
       5. The resin bead according to  claim 1 , wherein the elastomeric polymers are copolymers comprising repeat units from the polymerization of one or more conjugated diene and at least one unsaturated nitrile selected from the group consisting of acrylonitrile and methacrylonitrile. 
     
     
       6. The resin bead according to  claim 5 , wherein the elastomeric polymers are copolymers further comprising repeat units from the polymerization of one or more aryl monomers selected from the group consisting of styrene, p-methyl styrene, α-methyl styrene, tertiary butyl styrene and dimethylstyrene. 
     
     
       7. The resin bead according to  claim 5 , wherein the elastomeric polymers are partially hydrogenated. 
     
     
       8. The resin bead according to  claim 6 , wherein the elastomeric polymers are partially hydrogenated. 
     
     
       9. The resin bead according to  claim 1 , wherein the weight average molecular weight of the one or more elastomeric polymers is from about 6,000 to about 500,000. 
     
     
       10. The resin bead according to  claim 1 , wherein the elastomeric polymers are crosslinked. 
     
     
       11. The resin bead according to  claim 10 , wherein from about 5% to about 95% of the elastomeric polymers are crosslinked. 
     
     
       12. The resin bead according to  claim 1 , wherein the aryl monomers are selected from the group consisting of styrene, p-methyl styrene, α-methyl styrene, tertiary butyl styrene, dimethyl styrene, nuclear brominated or chlorinated derivatives thereof and combinations thereof. 
     
     
       13. The resin bead according to  claim 1 , wherein the copolymers in the dispersed phase contain repeat units resulting from the polymerization of one or more aryl polymerizable monomers with one or more monomers selected from the group consisting of maleic anhydride, maleic acid, maleimide, fumaric acid, C 1 -C 12  linear, branched or cyclic alkyl esters of maleic acid, C 1 -C 12  linear, branched or cyclic alkyl esters of fumaric acid, itaconic acid, C 1 -C 12  linear, branched or cyclic alkyl esters of itaconic acid, itaconic anhydride, ethylene, propylene, 1-butene, isobutylene, 2-butene, diisobutylene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, 3-hexene, vinyl acetate, C 1 -C 12  linear, branched or cyclic alkyl esters of (meth)acrylic acid, acrylonitrile, methacrylonitrile, and combinations thereof. 
     
     
       14. The resin bead according to  claim 1 , wherein the weight average molecular weight of the one or more homopolymers and/or copolymers containing repeat units resulting from the polymerization of one or more aryl polymerizable monomers is from about 10,000 to about 1,000,000. 
     
     
       15. The resin bead according to  claim 1  containing unreacted monomers at a level of less than 5 wt. % of the resin bead. 
     
     
       16. The resin bead according to  claim 1  further comprising a blowing agent. 
     
     
       17. The resin bead according to  claim 16  wherein the blowing agent is selected from the group consisting of nitrogen, sulfur hexafluoride (SF 6 ), argon, carbon dioxide, 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,3,3-pentafluoropropane, difluoromethane (HFC-32), 1,1-difluoroethane (HFC-152a), pentafluoroethane (HFC125), fluoroethane (HFC161) and 1,1,1-trifluoroethane (HFC-143a), methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, cyclopentane, neopentane, hexane, azodicarbonamide, azodiisobutyro-nitrile, benzenesulfonylhydrazide, 4,4-oxybenzene sulfonyl-semicarbazide, p-toluene sulfonyl semi-carbazide, barium azodicarboxylate, N,N′-dimethyl-N,N′-dinitrosoterephthalamide, trihydrazino triazine, mixtures of citric acid and sodium bicarbonate, and combinations thereof. 
     
     
       18. The resin bead according to  claim 1  having an aspect ratio of less than 10. 
     
     
       19. The resin bead according to  claim 1 , wherein the skin is from 0.1 to 7 μm thick. 
     
     
       20. Molded articles comprising the resin beads according to  claim 16 .